It is well known that delamination fracture between plies is a serious problem in composites. Three are three main techniques for reducing the tendency for plies to delaminate: interleaving (inserting a tough layer of material between prepreg plies), Z-pinning (inserting rigid cured carbon fiber/BMI resin rods (Z-pins) into the laid up uncured plies), and stitching the prepregs.
Each of these approaches has certain disadvantages, though. For example, Z-pinning is only applied to prepreg type materials and results in as tremendous loss of in-plane properties. Stitching increases fracture toughness at the expense of in-plane mechanical properties.
Nanomaterials are of great interest due to their special physiochemical properties dramatically different from properties from the bulk counterparts. Nanoparticle or nanofibers, including nanoclay platelets, carbon nanotubes, and graphene have played an important role as fillers in polymeric composites to enhance the mechanical, electrical and optical properties. Among new nanoparticles, Polyhedral Oligomeric silsesquioxane (POSS), which are silica-based nanoparticles have attracted much attention for the past ten years. These are silica nanostructures with the empirical formula RSiO1.5, where R may be a hydrogen atom or an organic functional group, such as alkyl, acrylate, hydroxide, or epoxide unit. It has been found that dispersing POSS nanoparticles into a polymer increases the strength, modulus, rigidity, and reduces the flammability, while retaining its lightweight and ductility.
Addition of nanofillers has the potential to drastically improve the mechanical and physical properties of composites. In some cases it might be dispersed in a polymer carrier (e.g., polyvinal pyrrolidone). This approach has been known to improve interlaminar fracture toughness by 100% or more. Improvement over reported values for CNT at much lower nanofiller contents has been reported. Among the types of nanoparticles that have been utilized include grapheme oxide and different polyhedral oligomeric silsequioxane (POSS).
Properties of POSS-containing polymer composites depend on the successful incorporation of POSS particles in polymeric matrices. There are two approaches to incorporate POSS particles into polymer matrices: (a) chemical crosslinking and (b) physical blending. In the first method, POSS nanoparticles are bonded covalently with the polymer. In the second approach, POSS nanoparticles are physically blended with polymer by melt mixing or solvent casting methods.
The effect of nanofillers depends on, among others, effective dispersion and interaction with the matrix (nanoparticle reactivity). However, no improvement is likely without using a polymer carrier, which might be explained by hydrogen bonding and interaction between nanoparticles and the matrix resin mediated by the carrier.
Additionally, there are several challenges that must be overcome in preparing POSS containing polymer composites, including long-range equilibration time, aggregation of nanoparticles, and costs that might be involved in large-scale production. However, if these issues could be resolved satisfactorily, the advantages would far outweigh the problems.
As is well known in the high performance composites arts, there has been a need for a system and method that provides a more effective way to create such composites and to make such composites more resistant to interlaminar fractures. Accordingly, it should now be recognized, as was recognized by the present inventors, that there exists, and has existed for some time, a very real need for an invention that would address and solve the above-described problems.
Before proceeding to a description of the present invention, however, it should be noted and remembered that the description of the invention which follows, together with the accompanying drawings, should not be construed as limiting the invention to the examples (or embodiments) shown and described. This is so because those skilled in the art to which the invention pertains will be able to devise other forms of this invention within the ambit of the appended claims.